Revision guide for unit 1 unit 4 - critical reasoning the structure and analysis of argument ocr as critical thinking. H042: critical thinking ocr as critical thinking online h042 f501 (2008-12) f502 (2008-12) ppq a2: argument elements by the end of this section. Unit 4 critical reasoning this book is designed to prepare you for the ocr as critical thinking examination revision tips from students.